High-energy gas fracture apparatus for through-tubing operation

ABSTRACT

The present invention discloses a high-energy gas fracture tool for through-tubing operation. The tool includes a blast head and a fracturing bullet connecting with the blast head. An electric detonator is provided in the blast head, and the fracturing bullet has a central pipe, which is sleeved by a fracture charge column and in which there is an explosive fuse sleeved by tubular igniting charge column. The present invention increases effectively charge amount per unit due to using no-shell bared fracture charge column, can attain combustion gas peak pressure quickly and increases energy utilization factor during fracturing because of utilizing blasting energy of explosive fuse and combustion energy of igniting charge. The present invention has better application effect, reliable and safe working. Moreover, the present invention may be used for fracturing or plug removal without tubing.

TECHNICAL FIELD

The present invention relates to oil exploration field, in particular to a high-energy gas fracture apparatus for through-tubing operation.

BACKGROUND OF THE UTILITY MODEL

During oil exploration, a high-energy gas fracture apparatus is a combustion-explosion apparatus, which applies a large magnitude of high-temperature and high-pressure gas generated by powder combustion to oil-gas bed, so as to remove plug and cause the strata near well to come into being a plurality of micro-cracks, thereby achieving the purpose of increasing production and injection.

High-energy gas fracture apparatus in prior art mainly use a charging structure with a metal housing or non-metal housing. However, such products can be only adapted for oil-gas well with a larger diameter. Chinese Patent No. CN 2170371 discloses a high-energy gas fracture multi-purpose generator, in which a bidirectional exhaust pipe not only is a charging vessel but also serves to release pressure. Such high-energy gas fracture apparatus employing charging structures with metal housing or non-metal housing have a relatively great outer diameter, and are difficult to be dropped into a predetermined layer through a tubing to perform the fracturing operation. On the contrary, such high-energy gas fracture apparatus can be used only before the tubing is dropped into a well or after a tubing string is lifted out from a well. Therefore, it is required many working procedure that the operation is complicated, and it is also difficult to control a well head when the stratum pressure is high. According to the known product structural principle, in order to pass through the oil-tubing, the charging amount must be decreased so as to reduce the outer diameter of the fracture apparatus. Because the charging amount per unit length is decreased, and the pressure elevating velocity of gas generated by the original igniting structural is slow, it can't be assured of necessary fracturing energy and operation effect. So far, no high-energy gas fracture tools for through-tubing operation have been proposed.

SUMMARY OF THE INVENTION

The present invention is directed to provide a high-energy gas fracture apparatus for through-tubing operation.

For this purpose, this invention provides a high-energy gas fracture apparatus for through-tubing operation, which comprises a blast head, a fracturing bullet connected with the blast head and an electric detonator provided in the blast head, the fracturing bullet having a central pipe sleeved by a fracture charge column outside and containing an explosive fuse sleeved by tubular igniting charge column inside.

In operation, the present fracture apparatus is dropped to a predetermined position in a well, and then the fracture apparatus is supplied with electrical power to cause the electric detonator and thus the explosive fuse to be detonated. The explosion energy generated by the explosive fuse ignites the igniting charge in the central pipe, and the combustion energy of the igniting charge ignites the fracture charge outside the central pipe through the cracks on the central pipe. The impinging of combustion gas generated by the fracture charge applies impact load to terrane at a relatively high speed, so that a number of cracks are formed in the terrane along a passage of each injecting hole.

A balance weight may be additionally provided on the blast head, so that the cable can be prevented from moving upwardly or twisting due to high pressure generated in the well cylinder.

Annular grooves and/or axial grooves may also be arranged on the wall of the central pipe, which serve as stress grooves, and is advantageous for the central pipe to be cracked upon igniting and detonating, so that the releasing manner of igniting charge energy can be adjusted in the central pipe, so as to enable control of the working pressure and time of the gas fracture apparatus.

Bared fracture charge column without sheath is used in the present invention, so that charging amount per unit length is effectively enhanced. Because of igniting by explosion energy of explosive fuse and combustion energy of igniting charge, the fracture charge column is directly ignited through cracks of the central pipe, combustion gas peak pressure is reached quickly and therefore energy utilization rate during fracturing is effectively enhanced, which is advantageous for fracturing rocks. The present invention has better effect in practice and ensures reliable and safe operation. Moreover, the present invention may also be used for directly fracturing or plug removal in an oil-gas well or a water-injected well without tubing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a generally structural view of this present invention;

FIG. 2 is a structural view of the fracturing bullet shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a preferred embodiment of the present invention. The present fracture apparatus comprises a cable connector 2, a balance weight 3, a blast head 4 and a fracturing bullet 6, which are sequentially connected. The fracturing bullet 6 has a plurality of segments connected by pipe joints 7. A lower end of the last segment of the fracturing bullet 6 is connected with a bottom blocker 8. An electric detonator 5, which is connected with a cable 1, is provided in the blast head 4. The fracturing bullet 6 comprises a central pipe 12, an explosive fuse 10 provided in the central pipe 12, a tubular igniting charge column 11 sleeved around the center portion of the explosive fuse 10, and a fracture charge column 13 located outside the central pipe 12, with both ends of the explosive fuse 10 in each segment of the fracturing bullet 6 being enclosed with a detonation transmission tube 9. Three axial stress grooves are arranged on the wall of the central pipe 12 with regular interval. After the present fracture apparatus is dropped to a predetermined position in a wall by means of a cable, the fracture apparatus is supplied with electrical power to detonate in such way that the electric detonator 5 detonates the explosive fuse 10 arranged in an igniting structure, then the explosion energy generated by the explosive fuse 10 ignites the igniting charge, and the combustion energy of the igniting charge ignites the fracture charge through the cracks on the central pipe 12. Because the igniting energy is strong, and the igniting time difference between each segment of the fracturing bullet 6 is small, the impinging energy of the generated combustion gas applies impact load to terrane at a relatively high speed, so that a number of cracks are formed in the terrane along a passage of each injecting hole. During the whole high temperature and high pressure process, blocking impurity in original seepage gap can also be removed, and seepage flow rate can be recovered and increased. 

1. A high-energy gas fracture apparatus for through-tubing operation, comprising a blast head, a fracturing bullet connected with the blast head and an electric detonator provided in the blast head, the fracturing bullet having a central pipe sleeved by a fracture charge column outside and containing an explosive fuse sleeved by a tubular igniting charge column inside.
 2. The gas fracture apparatus in accordance with claim 1, wherein a balance weight is provided on the blast head.
 3. The gas fracture apparatus in accordance with claim 1, wherein an annular groove is provided on the wall of the central pipe.
 4. The gas fracture apparatus in accordance with claim 1, wherein an axial groove is provided on the wall of the central pipe.
 5. The gas fracture apparatus in accordance with claim 3, wherein an axial groove is provided on the wall of the central pipe.
 6. The gas fracture apparatus in accordance with claim 2, wherein an annular groove is provided on the wall of the central pipe.
 7. The gas fracture apparatus in accordance with claim 2, wherein an axial groove is provided on the wall of the central pipe.
 8. The gas fracture apparatus in accordance with claim 6, wherein an axial groove is provided on the wall of the central pipe. 